Insulated reinforced circuit breaker contact bar



April 6, 1948. 2,439,084

INSULA iED REINFORCED CIRCUIT BREAKER conmcw BAR' H. c. GRAVES, JR 7 2Sheets-Sheet 1 Filed Dec. 28, 1944 III] PLAST/CMAT'k/AL IIIIl/IIIII/III/I [III/1111111 iIIII/IIIIII I III/IIIIIIIIII IIIII/IIIIIIIIIII/I,

IN VEN TOR. HERBERT C GRA m JR Arron/var April 5, 1948- H. c. GRAVES, JR2,439,084

INSULATED REINFORCED CIRCUIT BREAKER CONTACT BAR Filed Dec. 28, 1944 2Sheets-Sheet 2 I N V EN TOR. HERBEP T 6: 624 via" JR. /z BY Ar-mmrsyPatented Apr. 6, 1948 BREAKER CONTACT BAR Herbert C. Graves, J r., WestChester, Pa., assignor to I-T-E Circuit Breaker Company, Philadelphia,Pa., a corporation of Pennsylvania I Application December 28, 1944,Serial No. 570,095 3 Claims. (Cl. 200166) My present invention relatesto contact bars for circuit interrupter-s and more particularly to anovel reinforced insulated contact bar for carrying the movable contactarm of circuit breakers, switches and the like.

More specifically, my invention contemplates a novel contact bar andmethod of producing the same wherein said contact bar has a number ofreinforcingv metal inserts, preferably of steel, where the insertsextend longitudinally through the bar and are spaced from each other byin-.

sulating plugs which prevent any accidental conduction of currentthroughthe contact bar. Such contact bars may be of various length dependinglem existed, no method for solution thereof has been obtained. Myinvention provides a novel method for manufacturing such insulatedcontact bars in long lengths which may be cut apart,

while nevertheless retaining the steel inserts with on the number ofpoles which the circuit breaker or switch is intended to control and maybe designed to carry one or a plurality of movable contact arms.

My invention also contemplates a construction of such an insulated steelreinforced contact bar and method of making the same whereby saidcontact bars maybe made in relatively long lengths and cut off asdesired to predetermined lengths while nevertheless maintaining the fullinsulation between metal inserts and the full insulation of the contactbar itself.

Essentially in the manufacture of my novel contact bar, the insulatingplugs are threaded or forced into steel inserts in order to furnish amandrel oi sufiicient length to fit a wrapping machine and to takeadvantage of the full operative width thereof. After the wrappingoperation, the mandrels are processed and cut off to proper length, carebeing taken that the cuts fall in the center of the insulating plug. Thewrapping is, of course, done with suitable insulating material such asuncured plastic products. After the processing and before the mandrelsare cut apart to desired lengths, the cured plastic exterior becomesfirmly bonded to the metallic insert and the material of the insulatingplug, during the curing process. The metallic reinforcing insert, byreason of the knurling or scoring or other formation of the metallicinsert, provides a suitable anchor for the plastic covering.

It has been customary previously to make these contact bars individuallyand insert the insulating plugs at a subsequent operation. This is aslow, tedious and unsatisfactory method since machine capacity isadequate for multiple use. Inasmuch as it was necessary to have acompletely insulated bar yet to retain the steel insert for strength, itwas necessary to devise satisfactory means for including the plugs inthe original processing. However, although this probthe insulating plugsbetween them in order to increase the creepage distance between themetal inserts.

A primary object of my invention therefore is the formation of aninsulated contact bar reinforced by metallic inserts separated byinsulating plugs.

Another object of my invention is a novelprocess for manufacturing longlengths of insulated contact bars which may readily be cut apart intodesired lengths and which may have steel inserts properly located andimbedded in. plastic.

These and many other objects of my invention will become apparent fromthe following description and drawings in which:

Figure 1 is a longitudinal view in section of my novel steel reinforcedcontact bar.

Figure 2 is a fragmentary view in perspective partially broken awayshowing a portion of the novel insulated contact bar of Figure 1.,

Figure 3 is an expanded view showing the relationship between theinsulating plug and the metal reinforcing insert of the contact bar ofFigure 1.

Figure 4 is a cross-sectional view showing an alternative shape for themetal reinforcing insert of the contact bar of Figure 1.

Figure 5 is a fragmentary view in perspective partially broken awayshowing an alternative shape for the exterior of my novel contact bar.

Figure 6 is a fragmentary view in perspective partially broken awayshowing another slight modification which the shape of the metal insertof my novel contact bar may take.

Figure 7 is an expanded view in perspective showing the ends of a pairof adjacent steel inserts of my novel contact bar and insulation plughaving tapered ends which may be forced into drilled holes in the end ofthe steel insert. Figure 7 shows the preferred form which the steelinsert and insulating plugs of my invention should take.

Figure 8 is a view in perspective showing my novel contact bar in usecarrying contact arms in a circuit interrupter.

Figure 9 is a schematic view in perspective showing a step inthe processof manufacturing my novel contact bar.

Referring now to Figure 1, I have here shown in longitudinal section 'asimplified view of my aesaoee novel insulated contact bar whichillustrates not only the construction thereof but suggests a method ofmanufacture therefor. The exterior II of my novel insulated contact barI is of plastic material. The insulated contact bar It is rigidified andstrengthened by a number of longitudinal metallic inserts H2, H2separated by the insulating plugs I3, i 3. 1

Each end of each metallic insert i2 is provided with a threaded openingI5 to receive the threaded end iii of the insulating plugs I3. The mainbody of each insulating plug it has a diameter the same as that of themetal insert I2. Consequently when the threaded end I6 of the insulatingplug I3 is screwed into the threaded opening I5 of the metallic inserti2, the outer surface of the metallic insert I2 and the insulating plugI3 are continuous.

As the metallic inserts I2 and the insulating plugs I3 are threadedtogether as shown in Figure 1, a continuous outer cylindrical surface isformed by the adjacent members l2, I3, 2, I3, i2 which are screwedtogether. The insulation material for the entire contact bar may then bereadily wound about the entire length of the mandrel formed by thecombination of the metallic inserts I2 and it until the desiredthickness of insulation material is obtained. The entire contact bar maythen be fused and shaped to form.

After it is thus formed, the bar may be cut to appropriate length bycutting across the center of any insulated plug it as indicated at ofFigure 1. This will produce the result shown in Figure 2, which showsthe end of a contact bar which has been completed and is ready for use.

Figure 2 emphasizes the fact that the principal circumference of theinsulating plug l3 matches that of the metallic insert i2 to produce acontinuous mandrel on which the insulation II may be wound and formed.In Figure 2 it will be seen that although the insulation material isoriginally circularly wound around the mandrel l2, it may be shaped to arectangular form by the fusing processes (which are well known in theart). The resins in the plastic sheet material which is wound around theman-' drel (consisting of metallic inserts i2 and plugs I3) aresuflicient when the plastic is cured and shaped to cause the plastic toadhere very closely to the material of the insulating plugs I3. Thesurface of the metallic inserts 82 are knurled, scored or otherwiseshaped or indented to provide a suitable anchor for the plastic.

The relationship of adjacent metallic inserts l2 to the insulation plugsI3 between them is also more readily seen in the expanded view of Figure3 which shows an insulating plug I3 about to be inserted by threading anend I8 thereof into the tapped hole I5 of one of the inserts I2. Theother insert I2 may then be threaded over the other threaded extensionI8 of the insulating pl g.

The steel inserts I2 and the insulating plugs I3 may have any suitablecross-sectional shape and the exterior of the insulated contact bar mayalso have any suitable shape as may be required for the particularapparatus in which the same is to be incorporated. Thus, as shown inFigure 4, the insulating plug H3 is shown with a hexagonalcross-section, while the insulation coating III on the steel insert andinsulating plug 3 is of square cross-section.

As seen in Figure 5, the steel insert II2 is of hexagonal cross-sectionwhile the insulating plug it is of the shape previously described incon- ,nection with Figures 1 to 3. The exterior Bakelite coating 2H is.however, also of hexagonal cross-section. The shape of the formingapparatus in which the entire unit is fused predetermines the outsideshape of the contact bar.

As shown in Figure 6, the steel insert 3l2 may be of squarecross-section, while the exterior 3!! of insulation material may also beof square cross-section with the insulating plugs it having the samecylindrical shape as that shown in Figure 3.

The preferred construction for the metallic insert is the squarecross-sectional form of the insert 3I2 of Figure 6. This provides aninsert with greater strength and there is alsoless tendency for theinsulating material to be torn away from a square steel insert than around one. This tendency of the insulation to separate from the metallicinsert is due'to the high torque to which the insulated contact bar maybe subjected. However, as shown in Figure 6, where an insert plug I3 isused having the shape of the insert plug I3 of Figure 3, the squarecrosssection metallic inserts are spaced from each other by round plugsections. Where the plug ends I6 are to be threaded into tapped recessesat the ends of the metallic insert, then the main body of the plugs l3must be round in order to avoid dificulties in alignment.

Since, however, the very best construction would include steel insertsof square cross-section connected together by plugs also of square crosssection, this result is achieved by the construction shown in theexpanded view of, Figure 7, which shows steel reinforcing inserts M2, M2ofsquare cross-section, and an insulating reinforcing plug 3 also ofsquare cross-section. The corners of the square metallic insert may berounded to avoid dielectric stress which may otherwise occur at sharpcorners. The insulating plug M3 is provided at each end with the taperedprojections M6, M6 which may be forced into the cylindrical non-tapereddrilled holes M5, M5 in each end of the metal insert 2.

Neither the projections 6 nor the drilled holes 6 are threaded. Theprojection M6 tapers from a diameter slightly less than the diameter ofthe drilled hole M5 to a diameter just slightly greater than thediameter of the drilled hole 585.

The material of the insulating plug H3 and its projections tilt is,however, while stiff and rigid, nevertheless suficiently compressibleunder suflicient force so that the tapered projection e I 6 may beforced into the drilled opening M5 so that the end surface of theinsulating plug M3 from which the tapered projection 6 projects is insurface to surface relation with the end surface of the steel insertwhich has the recess or opening M5.

By avoiding the necessity for using threads, perfect alignment may beobtained between the surfaces of the body of the insulating plugs M3 andthe surfaces of the metal inserts 4I2 so that a continuous supportinginsert structure of square cross-section may be formed. This insertstructure, when formed,'may then be coated with an insulating materialin the same manner as that previously described in connection withFigures l to 6. This continuous square insert with square metal insertsof square metal plugs is, as has above been mentioned, preferred overthe knurled round one because ofits greater strength, also for thereason that the insulation material will i not be readily torn awayowing to the torque. similarly, a continuous square cross-sectionsupporting structure for the interior of the insulated contact bar ispreferred over a series of square metal inserts with round plugs,because it provides a continuous unit with continuous surfaces which mayreadily be covered with insulation, and which is almostsubstantiallycontinuous and strong.

In Figure 8, I have shown the manner in which an insulated contact barof the type shown in any one of Figures 1 to 7 may be used'in anordinary circuit interrupter. The contact bar it has been cut oif from alonger length so that the surface of the insulating plug l3 at eitherend The contact arm 5! carries pivotally mounted thereon around thepivot 503 appropriate contact structures 504 to which appropriateconnections may be made through the pigtail 505.

One of the contact arms 5M, preferably the center one, is connected tosuitable operating mechanism by means of which that contact arm andhence the insulated contact bar It) and the other contact arms may berotated in either direction to open or close the circuit.-

It is obvious that if a contact bar of a length necessary for only a onepole circuit breaker were needed, then the metal insert would have to bereduced in length to accommodate this smaller size circuit breaker and anew register, for cutting oif the bars, would be needed. It would benecessary to redesign the metal inserts for any variation in the size ofthe circuit breaker.

By means of the present invention, the entire operating width of awinding machine may be used to construct a long length of insulatedcontact bar which may then be cut up into appropriate lengths. Thus, asshown schematically in Figure 9, a mandrel structure 600 comprisingmetallic insert pieces l2, l2 and insulating plugs I3, I 3 may bescrewed together into a long length substantially equal to the width orcapacity of the winding machine so that the insert structure will havethe form of the insert structure shown in Figure 1. The entire mandrel600 thus formed may be mounted between the chuck 6M and tailstock 602 ofthe winding machine, and the plastic treated material 605 may be woundthereon.

When the winding of the insulation is completed to the requiredthickness, the insulating contact bar thus formed may be cured bymolding to the desired shape so that the plastic windings will becomehomogeneous with each other and be secured to the insulation plugs andto the metallic inserts and so that an appropriate shape may be formed.Thereafter, the completed long length of insulated contact bar may becut apart, as previously described in connection with Figure 1, bycutting through the center of the insulating plugs l3.

Further, in the assembly shown in Figure 8,

the steel bar should not extend to the end of the phenolic or otherplastic coating, since it would be too close to the contact arm 50!;thus a continuous steel bar cannot be raised and cut off because thenthe steelwould extend to the end of the bar.

Previously. it has been customary to use a circular steel-bar and toinsert an insulating plug that would extend some distance in from theend of the bar. Efforts to glue such a plug inposition after the entirebar had been made were not satisfactory. Also, various insulatingcompounds were used to fill up the end of the phenolic bar as additionalinsulation. This material often softened under the temperatures to whichthe circuit breaker was subjected and thus ran out and interfered withthe operation of the breaker. Further, it did not form a completeinsulation. Since the steel insert had to extend fairly close to theends of the bar so as to be included in the clamping action of the twooutside pole parts, the recess [for the insulating plug was relativelyshallow. Also, after a steel piece had been inserted into the phenolictube, it was difiicult thereafter to insert a plug which would be tightand sealed in to prevent a breakdownon dielectric tests. I

My novel process and the construction produced thereby avoids all ofthese difilculties, The plug can be short because it is tightly sealedin the wrapping. Further, the insulating plugs may be uncured whenwrapped and cured during the curing process of the wrapping.

Further. it should be understood that in present molding thickness, itis practically impossible to properly locate inserts completely embeddedin a plastic for reinforcing purposes without having-them float duringthe molding operation. My novel process overcomes this diihculty, andthe reinforcing insert of my invention may be located and maintained inits exact location during the molding operation without having someportion of the metal extend outside the molding after the operation iscompleted.

This method further permits the construction of insulated pull rods forsolenoids. In the case of solenoids, the steel parts would projectbeyond the tubing at both ends for a pull operation. The spacing plugsseparate and insulate from each other the projecting pieces of steel.These projecting pieces of steel may be threaded. In

such case, the steel rods may be reduced in diameter at the end,threaded and screwed into the plug. Such pull rods for solenoids may, ofcourse, be made round or square or of any suitable cross section.

It will be obvious that in all of the constructions above shown, theplugs of insulating material maybe provided with openings; and the metalmembers may have the extensions for insertion in the openings of theplugs.

By means of my novel construction and methad, I have devised a novel andsimplified insulating contact bar having a plurality of spaced metailicinserts separated by insulating plugs whereby the insulated contact baris completely reinforced while no continuous current path through theinsulated contact bar is provided. My invention is adapted to the makingof long or continuous lengths of such insulated contact bars which maythereafter be readily cut apart to desired separate lengths, whileretaining allof the initial characteristics.

In the foregoing, I have described my inven tion only in connection withpreferred embodiments thereof. Many modifications and variatlons willnow be obvious to those skilled in the art; accordingly, I prefer to bebound not by the specific disclosures herein but only by the appendedclaims.

I'claim:

1. The method or manufacturing contact bars which comprises the screwingof threaded insulating plugs into steel inserts to form a mandrel ofpredetermined length to fit a wrapping machine, wrapping andmolding-insulation material on the mandrel and cutting the mandrel withthe insulation wrapping into predetermined lengths,

- the cuts falling in the center of the insulating plugs and bonding theplugs to the steel inserts.

2. The method or making insulated contact bars with reinforcing metalinserts which comprises securing the reinforcing metal inserts to theinsulating plugs using the assembly of metal reinforcements andinsulating plugs as a man drel for applying longitudinal insulation andmolding the insulation thereto.

3. A contact bar for a circuit interrupter consisting of an elongatedmetallic reinforcing member attached to an aligned insulating member ateach end, said reinforcing member having a socket at each end internallythreaded,

each or said insulating members having threaded extensions engaging theassociated internal threads of said reinforcing members and having Ienclose the reinforcing member.

mam c. GRAVES, .111.

REFERENCES cr'rm The following references are of record in the file oi.this patent:

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